Marion,
It depends on what kind of music career you want to get going. If you merely want to work in and around Toronto, then yes you would have a problem moving about, but if you want to tour, I'm afraid the only thing you will be restricted from doing is being at home. I have been on the road for fourteen years now and I have lived loads of places, and found that it really doesn't matter where you live as you rarely see it!
As a session musician you would also have to travel, and the best thing to do would be to build up a CV of sessions you have done, get a website, people will get in touch if you're good. I don't see any barrier to moving about there either.
If you wanted to leave music for a couple of years your profile would go down a little, but if you have a catalogue that is out there and available it will never quite go away. You can keep chasing and chasing the "momentum", wear yourself out: what's the point in that?
Good luck anyway. Canada and America are huge places to work in, so hard to get your head above the crowd. Plenty of tasty road though!
cheers,
ec